1. Field of the Invention
The present invention generally relates to clamp structures capable of securing concentric tubular members together at or near a slip-joint and additionally capable of forming a low-leakage connection between such tubular members. In particular, the invention relates to a ring clamp capable of forming an essentially gas-tight 360.degree. indentation in such a tubing slip-joint and acting to secure the joint.
2. Description of the Prior Art
Clamping structures capable of securing concentric tubing together at a slip-joint are well known, one well known exemplary structure taking the form of a U-shaped bolt member with a saddle member respectively receiving the legs of the bolt member within spaced tubular receptacles on said saddle member. The saddle member has an arcuate inwardly disposed edge surface, the contours of which complete a 360.degree. arc in concert with an arcuate back portion of the U-shaped bolt. A circular perimetric surface thus formed is capable of impressing a 360.degree. bead into concentric tubing to form a substantially gas-tight seal, the clamp further securing the tubing together. One particularly useful clamp which exhibits such capability is the structure disclosed in U.S. Pat. No. 3,955,250 by Heckethorn, this structure being particularly suited to heavy duty applications, that is, for applications where torque levels applied to the clamp must typically range from 40 and 80 foot-pounds in order to meet critical sealing requirements associated with anti-pollution devices installed in presently available motor vehicles. Many slip-joints on exhaust piping need not be secured with so great a torque but still demand substantially leak-free performance. Such clamps must also be low in cost, of a small size and light weight, and be easily installable. Clamps presently in use for such applications exhibit certain of these characteristics but no such clamp which has been heretofore known has provided all of these characteristics and has further been capable of eliminating gas-leakage at the slip-joint.
Brown, in U.S. Pat. No. 3,109,215 discloses a ring clamp which is tensioned about a slip-joint by only a single nut cooperating with a threaded leg portion which extends from one end of a discontinuous ring member. The ring member of Brown has a first end which includes an end face generally tangential to the inner circumference of a main circular portion of the clamp. The Brown structure is further seen to have side portions which are formed with generally circular upper edges of "slightly greater radii" than that of the inner circumference of the ring member, and located so that only the ring member itself is adapted to engage the telescoping tubing being secured and sealed. As will be seen from the following, the present invention provides a ring-like clamping structure tensionable by a single nut and comprising a main ring portion having an end face which is not tangential to the inner circumference of the ring portion. Further, in the clamping structure of the present invention, the inner circumference of the main ring portion and the inner circumference of an associated lug member fitting within a discontinuity in the ring portion are identical, both the ring portion and the lug member contacting the tubing which is to be secured and sealed. The structural differences taught by the present invention occasion a substantial difference in sealing capability, the present structure exhibiting virtually 0-leakage at 20 foot-pounds nut torque at pressures of 15 psi. Similar clamps which are available and including those clamps which are now standard equipment on presently available motor vehicles have leakages in excess of 18,000 SCCM under the same test conditions. Such dramatic sealing function essentially results from an application of pressure by the present clamping structure about the full 360.degree. circumference of the tubing joint.
Powell, in U.S. Pat. No. 2,093,210, discloses a clamping member having a flattened end portion which is attached to the clamping member with a rivet. While the Powell clamping member contacts the tubing for a relatively greater percentage of the total tubing circumference than does the Brown structure, the spaced structure of the Powell clamp results in leakage paths due to the provision of a narrow sealing bead which is limited to 270.degree.. The full 360.degree. gas-tight seal indentation provided by the present invention results in a previously unattainable sealing effect for such a simple light-weight and low cost structure.